The invention relates to a device for air-conditioning the passenger compartment and for cooling the drive system of electric vehicles and, more particularly, to a device having an air-guide duct which is connected on the inlet and outlet sides to the passenger compartment. The duct exhibits a controllable fresh-air opening and contains at least one fan for the generation of an air current in the air-guide duct. The device further has two heat exchangers disposed one behind the other in the air-flow direction in the air-guide duct, one of which, together with a circulating pump and a cold store, is incorporated within a circuit of a cold-transporting medium. The circuit is run via an evaporator of a refrigeration unit. The other heat exchanger, together with a circulating pump and a heat store, is incorporated within a circuit of a heat transporting medium, which circuit is run via the drive system of the electric vehicle for vehicle-cooling purposes.
In vehicles having a combustion engine, the waste heat given off by the combustion engine after the engine has warmed up is greater than the energy requirement needed for heating the vehicle, even on cold winter days. In the case of electric vehicles, although there is also a certain dissipated heat generated in the drive system, comprising an electric motor, transmission, battery and power electronics, the quantity of heat is not sufficient for performing a heating operation under low external temperatures.
It is known from German Patent document DE 42 06 611 A1 to provide in the heat-transporting medium circuit for the heating-specific heat exchanger an additional heat store. The heat store is both heated up whenever the drive battery of the electric vehicle is charged, and takes up excess waste heat from the drive system which is not required for the heating operation. In the event the heating requirement substantially increases, the heat store is called upon, as an additional supplier of heat, to heat up the air supplied to the passenger compartment. In order to save energy, the air is in this case extracted from the passenger compartment in a circulating-air circuit, heated up in an air-guide duct, mixed with fresh air, and fed back to the passenger compartment. For cooling the air in summer operation, the air in the air-guide duct, the heating-specific heat exchanger having been switched off, is guided through a second heat exchanger, which, together with a cold store and the evaporator of a conventional refrigeration unit, is disposed in the circuit of a cold-transporting medium. Here, too, the cold store serves to save energy for the refrigeration unit. This is because when the cold requirement is low, the storage capacity of the cold store is sufficient for air-cooling purposes and obviates the need to switch on the refrigeration unit, with its energy-consuming compressor and condenser.
In the case of electric vehicles, in order to obtain a large journey range in addition to the energy saving in the auxiliary systems, such as the air-conditioning system, a great deal of attention should also be paid to obtaining the lowest possible weight for these auxiliary systems. If heat and cold stores are to possess a sufficiently large storage capacity, then they also together constitute a considerable extra load for the electric vehicle.
There is therefore needed a device for air-conditioning the passenger compartment and for cooling the drive system of electric vehicles, which has a reduced total weight by economizing on heavy structural components.
These needs are met by a device having an air-guide duct which is connected on the inlet and outlet sides to the passenger compartment. The duct exhibits a controllable fresh-air opening and contains at least one fan for the generation of an air current in the air-guide duct. The device further has two heat exchangers disposed one behind the other in the air-flow direction in the air-guide duct, one of which, together with a circulating pump and a cold store, is incorporated within a circuit of a cold-transporting medium. The circuit is run via an evaporator of a refrigeration unit. The other heat exchanger, together with a circulating pump and a heat store, is incorporated within a circuit of a heat transporting medium, which circuit is run via the drive system of the electric vehicle for vehicle-cooling purposes. The cold and heat store is formed by a single energy store, which, by means of at least one switchover valve, can be switched alternately into the cold-transporting-medium or heat transporting-medium circuit, and in that, as the cold- and heat-transporting medium, the same liquid transmission medium is used.
The device according to the present invention has the advantage that, as a result of the union of the cold and heat stores, a saving is achieved both in terms of bulk and in terms of considerable structural weight, i.e. the total device becomes substantially lighter, thereby contributing to an improved energy balance for the electric vehicle and hence to an extension of the vehicle range. Conversely, where the electric vehicle already has a sufficiently large trip range, both the storage capacity of the heat store and the storage capacity of the cold store can be doubled as a result of the common energy store for the cold-transporting-medium and heat transporting-medium circuits. The entire storage capacity of the energy store is fully available in the cold period, during heating operation, as a heat store, and in the hot period, during cooling operation, as a cold store. The capacity of the energy store is thus constantly fully utilized and in no operating mode is there a dead weight present.
According to a preferred embodiment of the invention, the energy store is arranged such that it is connected directly downstream of the heat exchanger in the cold-transporting-medium circuit and directly upstream of the heat exchanger in the heat-transporting medium circuit, in each case viewed in the direction of flow of the transmission medium. In this manner, on the one hand the stored heat energy is directly available for the heating and, on the other hand, the just started-up refrigeration unit with the stored cold is brought to a favorable operating point in a particularly short period of time.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.